In general, inkjet printing machines or printers include at least one printhead unit that ejects drops of liquid ink onto recording media or an image forming member. A phase change inkjet printer employs phase change inks that are in the solid phase at ambient temperature, but transition to a liquid phase at an elevated temperature. A mounted printhead ejects drops of the melted ink to form an ink image. The ink can be ejected directly onto print media or onto an image receiving member before the image is transferred to print media. Once the ejected ink is onto the media or image receiving member, the ink droplets quickly solidify to form an image.
During operation of the printer, printheads may emit ink that flows over a face of the printhead instead of being ejected toward the image receiving member. For example, a controller in the printer operates one or more devices to purge and clean printheads to ensure that the ink ejectors in each printhead operate efficiently. The printhead purging urges ink through the inkjet ejectors of a printhead to remove debris, air bubbles, or other contaminants from the inkjet ejectors. The purged ink emerges from the nozzles of the ejectors and flows down the front face of the printhead. A drip bib positioned beneath the front face collects the purged ink and directs the ink into an ink receptacle. The controller operates actuators to move the ink receptacle into position to receive the purged ink and, following the purging and cleaning operation, operates the actuators to return the ink receptacle to a position where the receptacle does not interfere with printing operations.
The inkjet ejectors may also release ink in response to a printhead being activated after heat has been removed from the printhead for a period of time that enables melted ink to return to the solid phase. As the heaters in the printhead heat the printhead to a temperature that melts the solidified ink, the nozzles of the inkjet ejectors may “weep” ink. This ink flows down the face of the printhead and onto the drip bib. Because no cleaning operation is being performed, the ink receptacle is not positioned beneath the printhead during activation. Consequently, vibration in the printer may release the liquid ink from the drip bib. Once the liquid ink lands on another printer component, it is likely to freeze on the image receiving member or some other printer component in the vicinity.
As noted above, printheads typically include a drip bib positioned below each printhead. The lower edge of the drip bib tapers to one or more channels or points where ink collects prior to dripping into the receptacle. Although most of the purged ink falls from the collection areas of the drip bib, surface tension in a small portion of the purged ink may be sufficient to retain ink on the drip bib after the ink receptacle is no longer positioned below the drip bib. On occasion, this residual liquid ink may break free from the drip bib and land on a printer component. In some cases, the frozen ink may adversely affect the printer component on which the ink lands. Thus, more efficient removal of ink from drip bibs in printers using phase change ink is desirable.